To monitor safety and measure changes in ureagenesis resulting from gene therapy in patients with urnithine transcarbamylase (OTC) deficiency. OTC deficiency is an inborn error of urea synthesis inherited as an X-linked disorder. Current treatment relies on alternate pathway therapy or liver transplantation. A Phase I study of adenoviral mediated gene therapy is being carried out at the University of Pennsylvania on adult heterozygotes, with this disorder. We are a collaborating institution in this study and will perform in the GCRC: (1) heavy isotope (15N)/allopurinol studies to measure efficiency of the experimental treatment in correcting deficits in ureasynthesis; and (2) to obtain blood for liver, renal hemotologic, and immune function to study safety in objects with OTC deficiency.